User superuser with english language works nice, instead the same
User superuser with italian language
(note: I've re-read the documentation about Language configuration https://documentation.magnolia-cms.com/display/DOCS/Language+configuration and my Defining Locales configuration is the one I have always used and you can see in the image )
reports this problem:

Description of the Testcases :
1° Testcase)
Create a new web Page in Pages.
Try to delete it.

I get the following ERROR "Pulse Dashboard" and ful log in log-errore-cancellazione.txt:

2015-09-24 15:52:36,240 ERROR fo.magnolia.ui.contentapp.browser.BrowserPresenter: An error occurred while executing action [confirmDeletion]
info.magnolia.ui.api.action.ActionExecutionException: java.lang.IllegalArgumentException: Unmatched braces in the pattern.

2° Testcase)
Export a node in the demosite in Pages (eg: /demo-features/modules).
Try to Import at the same level. [This will generate ERROR same UUID. Instead doing this same operation with eng superuser it will correctly generate "PageName0" without errors.]
Try to Import in a different level. [This will work]
Try to delete the node you just imported. [This will generate the same error code as above]

NOTES:

• The 2° Testcase and relative error seems to apply in Assets too
• This is not a multisite structure-content related problem.